* Use iOS 13+ UINavigationBarAppearance for navbar styling
* various individual view controller navbar style tweaks and fixes
* Remove unused navigation bar styles
* rename 'default' style blur
* Apply blur style to the UIVisualEffectView generated by UINavigationBarAppearance
* Use iOS 12 navbar blur method on iOS 13 since its bugged
* Fix on iOS 15, use old method on iOS 14
* PR comment nits
* explicitly invalidate KVO observers
* make shouldCancelNavigationBack a var
* rename OWSNavigationView->OWSNavigationChildController
* forward delegate calls to OWSNavigationController
* apply theme and style to OWSNavigationBar consistently
fix themeing on gif picker controller
* Use topPinned navbar position. Size the blur effect view using the background view
* Use fade animation when hiding the navigation bar
* fix issues with reduced transparency setting
* pr feedback
